An embodiment relates generally to GPS-assisted positioning.
Global Positioning System (GPS) or other Global Navigation Satellite System (GNSS) receivers operate by tracking line of sight signals. These receivers typically require at least four or more satellites to be continuously available in an unobstructed line of sight of a satellite receiver on a vehicle. Due to natural and man-made obstructions (e.g., buildings) or natural obstructions (i.e., dense tree cover), the optimum number of satellites required to accurately determine a position of the satellite receiver may not be available under certain conditions. Other errors such as orbital errors of a satellite, poor geometry, atmospheric delays, multi-path signals, or clock errors may require more than a minimum required number of satellites available to accurately determine the position of the receiver. Determining relative positioning between two vehicles based on their respective GPS positions and measurements may also be inaccurate if the two vehicles have obstructions where a requisite number of common satellites are not available. Having only common satellites for relative position estimation can increase the accuracy of the relative position as it minimizes errors that are the results of measurement data from different satellites. What is needed is a method and system for overcoming the issue when a common number of satellites required for relative positioning between at least two vehicles are not present.